Most of the tennis rackets used today are designed with the main strings nearest the center of the racket being the longest in length with a gradual shortening of main string length as the main strings progress away from the longitudinal center of the racket.
As is well known, the longer the length of the main string, the more elastic (i.e. higher is the Coefficient of Restitution, C.O.R.).
The typical oval head-shaped racket in use today provides a greater C.O.R. than the round-headed rackets due to centralized location (i.e. no twist) and strength from the structural integrity and also permits the use of the longest main string length. This combination yields a large difference in C.O.R. as the ball is struck at various points on the racket, which occurs naturally during normal play.
The C.O.R., or power, in tennis rackets can also be increased by lowering string tensions. However, as string tension is lowered, there occurs a loss of control which affects the direction in which the ball may be hit. This greatly affects the playing ability of the racket itself.
The more experienced players use a tennis racket having a smaller head so as to increase the playability of the racket. Large headed rackets have been developed and are now on sale which increase the stability of the racket and, therefore, are much more usable by less experienced players.
It has been proposed in the past to improve the C.O.R. in tennis rackets as the ball impact departs from the longitudinal center line, that is, as it goes from side to side, by using a single inverted bridge in the throat of the racket, matching its contour with the contour at the top of the head. The purpose of this construction was to equalize the length of the main strings. While directionally correct, this construction was not sufficient to significantly improve off center performance, since C.O.R. falls off at a much faster rate. This is due to a combined effect of string length and moment of inertia of the racket about its longitudinal center line. What is required in order to significantly improve off center performance is to have the main strings increase in length as the impact point moves away from the center. This is the principal used in the present invention.
The present invention provides a racket which provides more uniformity with less than normal tension on the main strings. As a result of this, the racket provides less shock to the user, has a better life and has enhanced predictability. The racket of the present invention provides the playability of small headed rackets while still providing the stability of large headed rackets.